Work as a consultant in Canada

Hi

If my understanding of the whole work permit issue is correct, you need a work permit if you want to do work on Canadian soil, if you invoice for a project for which you need to be in Canada for the majority of the time (there are some exceptions like organizing seminars or teaching, if I'm right).
But when you apply for a work permit, you always need to be able to prove you're working for a Canadian employer. I am from Belgium and back there I am a self-employed consultant and I search my own customers. I want to do that here in Toronto as well.

However, this means that:
- I cannot really show contracts with Canadian employers because I currently only have prospects
- I probably will invoice through my Belgian company (unless there's another way of invoicing)

I have a visitor visa, I live in Toronto right now and I know I have to leave the country to change my status.
Does anybody have experience with my situation, knows what my possibilities are or have some valuable advice?

Regards
Gino Marckx